Apparatus and methods for detecting pump defects in a pumping system comprising multiple pumps. Each pump includes a pump fluid outlet fluidly connected with the pump fluid outlet of the other pumps. Pump defects are detected by generating information related to fluid pressure fluctuations at each pump fluid outlet and determining harmonic frequencies from the information related to fluid pressure fluctuations for each of the plurality of pumps. The amplitude of the harmonic frequencies is indicative of a defective one of the plurality of pumps.